The Stability of Oral Liquids

Many types of formulations both aqueous and non-aqueous are included among those which can be classified as oral liquids. Included in this group are syrups, suspensions, emulsions, colloids, mouthwashes, elixirs, and soft gelatin capsules. It will not be possible to cover in detail all the different formulations or factors which will effect their stability; however, those discussed should have some applicability to all systems. It is safe to say that, as a class of formulations, oral liquids are generally more complex in their composition than parenterals and, therefore, more interactions can occur which might affect the stability of the product. Not only is it necessary to consider the solution stability of the drug substance, but also the effects upon stability caused by such things as suspending agents, colorants, flavors and sweetening agents need to be addressed.